The present invention relates generally to a stitch pattern setting apparatus for an electrically driven sewing machine and, now particularly to an improvement of the stitch pattern setting apparatus of a type in which various sewing or stitch patterns can be alternately and mutually exchanged for use.
Generally, as shown in FIG. 1, a motor-driven sewing machine of the aforementioned to type is arranged such that a rotation shaft of the sewing machine MC is driven by a clutch motor MO, with a clutch disc CLB being disposed between a friction clutch disc CLM, fixedly mounted on an output shaft of the clutch motor MO and a friction brake disc BRM. When a clutch coil CL is electrically energized, the clutch disc CLB is brought into contact with the friction clutch disc CLM. On the other hand, when a brake coil BR is electrically energized, the clutch disc CLB is brought into contact with the friction brake disc BRM. The rotation shaft of the sewing machine MC has a pulley PL1 fixedly mounted at one end portion thereof, which pulley PL1 is operatively coupled to a pulley PL2 by means of a belt BL. The pulley PL2 is mounted on one end portion of a shaft, with the clutch disc CLB being fixedly mounted at the other end portion of the shaft. A synchronizer SY is mounted on and end of the rotation shaft of the sewing machine MC synchronizer SY serving to detect the number of rotation of the machine shaft as well as vertical positions (up and down positions) of a needle. The motor MO is provided with a controller CTR to which a pedal sensor PS is connected for detecting actuated positions of a foot pedal FP. The controller CTR has inputs supplied with signals representative of a stitch pattern and the number of stitches, respectively, which signals are produced by a stitch pattern setting apparatus PAT mounted on the lower surface of a machine table TB. As shown in FIG. 2 the controller CTR includes a microcomputer MCPU which receives as inputs thereto the pattern signal and the stitch number signal from the pattern setting apparatus PAT, a machine speed signal TG, the upper needle position signal UP and the lower needle position signal DOWN from the synchronizer TG, a forward switch signal FSW and a reverse switch signal RSW from the pedal sensor PS, and a speed set signal SSET. Based on the results of the processing of these input signals, the micro-computer MCPU controls the clutch coil CL through a transistor TCL, the brake coil BR through a transistor TBR and a stitch pattern repeating solenoid RV through an associated transistor TRV, whereby the sewing machine MC is so driven as to form the stitch pattern having a predetermined number of stitches sequentially and repeatedly set at the pattern setting apparatus PAT. Since the machine driving system of this type is well known in the art, any further description is considered unnecessary.
As shown in FIG. 3, the known pattern setting apparatus PAT includes a rotary switch RSW1 for selecting a desired stitch pattern and a digital setting switch RSW2 for setting the number of stitches for respective pattern elements constituting the selected stitch pattern. The digital setting switch RSW2 includes decimal one-digit counters or switches 11, 12, 13, 14, 15 and 16, each capable of independently setting any desired number of 0 to 9. The rotary switch RSW1 is arranged to select one of three stitch patterns 1, 2 and 3 and the respective numbers of stitches for the pattern elements A, B, C and D, are set to any number of 0 to 9 by one-digit switches 11, 12, 13 and 14, respectively, while the numbers of stitches for the pattern elements E, F and G are set to any number of 0 to 99 by pairs of one-digit switches 11, 12; 13, 14 and 15, 16, respectively. In the case of the illustrated example, since the numbers of stitches for the pattern elements A, B, C, D and G are set at 4, 4, 4, 4 and 44, respectively, a complete stitch pattern 1 is formed through operation of the sewing machine MC in succession of the element A (4 stitches in the forward sewing direction), the element B (4 stitches in the reverse sewing direction), the element G (44 stitches in the forward direction), the element C (4 stitches in the reverse direction) and the element D (4 stitches in the forward direction) in this sequence. When the foot pedal is continuously pressed, the sewing operation is continued so that the stitch pattern 1 is repeatedly formed.
When a sewing operation is to be carried out by a single sewing machine in such a manner in which a set of different stitch patterns having different numbers of stitches are formed repeatedly, the corresponding change-over of the rotary switch RSW1 as well as the alteration of the values set by the digital switches has to be done every time the stitch pattern is to be changed which means that a correspondingly increased number of switch manipulations are required, involving less operation efficiency. Further, there may arise the possibility of erroneous operation such as erroneous setting of the stitch number.